Published UK Patent Application No. GB 2263817A concerns a process for the production of service boxes and their parts having new construction characteristics, format and design which fulfill the purpose for which they were specifically conceived with maximum safety and efficiency.
A service box for cars is a central mechanism of an electrical connection system in the vehicle. This service box acts as a support for protection equipment (fuses) as well as for various electrical components, such as relays, diodes, electronic control modules and connectors.
All the connections of the above mentioned components are effected in the box by means of one or various printed circuit boards (PCB's). The circuit boards and the terminals are covered with plastic which protects and secures them. The service boxes act as connection centers, grouping together the electrical and electronic connections, and are capable of distributing power and control signals to and from the various parts of the vehicle.
Certain aspects of the boxes referred to in the production process below have been described in Spanish Model No. 228,789 entitled "Electronic distribution box for cars", Spanish Model No. 239.279 "Perfected Electrical Distribution Block", Spanish Invention Patent No. 533.433 "Perfected procedure for the production of electrical distribution boxes", additional Spanish certificate No. 534.841 "Improvements in Invention Patent No. 533.433" and finally, Spanish Invention Patent No. 9001544 "Perfections to production procedure for electrical distribution boxes."
The above-mentioned documents contain some of the improvements applicable to electrical distribution boxes and the objective of UK Patent Application No. GB 2263817A is to amalgamate the improvements contained in the previous proposals into one construction which would embody the various parts and processes concerned in the production of these service boxes.
The service boxes are connected to the exterior by means of interconnections, which are metal parts embedded in copper and attached by solder. The main advantage of each new product (i.e. service box) lies in the versatility of its design, which allows adjustments or increase of function at low cost.
Amongst other advantages, these improvements, details of which are given below, include PCB technology, enabling:
a) Less weight than the traditional system
b) Less volume than the traditional system
c) Decrease in cost compared to present cable system
d) Easy assembly of service box in vehicle
e) Prevention of connection errors
f) Access to both the user and mechanic
g) Safe connections
The object of UK Patent Application No. GB 2263817A is to incorporate the improvements of the previous Spanish patents, together with the various parts comprising a general non-specific service box. The product or the service box is created in the design phase and produced according to the customer's requirements, adapting it to the technology described, which is common to all boxes.
With this object in mind, UK Patent Application No. GB 2263817A provides a process for the production of service boxes comprised of a set of PCB's to which have been inserted and soldered the corresponding electrical components, and characterized in that the production process includes at least some of the following steps: printing of components, soldering of components, insertion of bridges, insertion of short pins and long pins, checking of plane circuits, angling of PCB's by milling of bases, "sewing" of PCB's along perimeter edges, assembly of covers and fuses, final checking, encasing.
The production process for service boxes begins with the study of the product, paying special attention to technical and dimensional requirements of the customer. At this first stage, the printed circuit begins to take shape--whether on a multiple board, double sided, angled or otherwise--together with the plastic parts which serve to assemble, seal, attach and separate the boards. The external assemblies in the box, such as connectors, fuses and relays, are also examined at this stage.
The production of the PCB starts from a base with a conducting lamina, generally copper, on top. The base used is normally paper with phenol resins, called FR-2, although FR-4 (glass fibre with epoxy resin) can also be used for car service boxes. The conducting material is chosen for its thickness, depending on the amperage it must withstand; thicknesses up to 400 mm are commonly used.
An anti-solder film or varnish is then applied to the conducting material; the edges of the conduction strips are also oxidized for this purpose, as the anti-rust film does not reach them.
Electrical connectivity between the two sides of the circuit board is achieved by means of a short pin. Several layers joined together (a multiple board), which may be either single or double sided, are used to form service boxes. The boards are mechanically joined together by long pins, which also form an electrical connection. Four sides, each of copper, can then be connected by means of the long pins (two sides of one board connected to one of the other, the four sides together, or one of one board to one of the other).
The long pins are positioned around the external perimeter of the boards to achieve good mechanical connection, hence the insertion of these long pins is known as "sewing".
It is also possible for reasons of volume to use an angled circuit, so that less volume is occupied using the same surface. In this way, PCB's angled at 90.degree., 45.degree. and even 180.degree. are possible.
The plastic parts used are designed according to the requirements of the customer and the design of the PCB. The main plastic parts are the plastic supports (basically for fuses, connectors and relays).
The function of the plastic parts is to give mechanical support to the connections, relays and fuses and also to house the PCB, as described below. For a service box to be operative it must be set into the vehicle using screws, which go directly into the body work, or to feed through screws or suitable clips.
Separators are also used in the assembly for PCB's in the service box. Their purpose is to provide electronic insulation between opposing strips of multiple board PCB's.
To house relays, fuses and connections each plastic support must be designed so that the corresponding component fits into its housing. In this way a box is designed to provide a housing for fuses, connectors, relays and the extracting pincer.
The components of the PCB normally used in the recommended production processes are sockets. These are embedded in the board, and are pincer shaped. They generally hold the tab of a fuse, relay or other component, thus making an electrical connection. The tabs are components inserted into the board which act as an interconnection with the exterior, they are normally wide and long with respect to their depth. A group of tabs will form an external connection support socket. Bridges are mechanisms for connecting support sockets and for connecting strips of a PCB, when it is impossible to make the same union using the strips themselves due to shortage of space.
Jumpers are also used and have the same function as a bridge, as previously described, but join strips which are angled at 45.degree., 90.degree. and 180.degree.. They are soldered on the side in which they are inserted and do not cross the base.
Another element used is a busber, which is any type of bridge inserted into the PCB when it is not possible to use the conventional bridge described above, whether due to electrical reasons or because of electrical requirements. Finally, conducting screws are also used, their geometry and function will depend on what purpose they are required for.